More Basic Telephone Wiring Qs

[thescullster]

Hi all

Following on from my previous thread re: Higher Speed Broadband with FTTC, I am trying to establish what sort of loss of signal I am likely to get over my in-house "extension" cable.

The reason I have extension in quotes is because, although it is an extension of the supplied incoming phone line, it is before the face plate splitter and router/phone distribution panel bit.

Q1: what is the construction of the incoming phone line supplied by KC likely to be? Is this twisted pair or simply 4 core telephone cable? If it makes a difference, the house is early 70s with an underground connection (supplied by Kingston Communications) right into the hallway master box.

Q2: if I use my existing installed telephone cable between the master box and the loft, what additional losses would be incurred on the signal before it made it to the new splitter/router (as compared to installing the splitter at the current master box hall location and connecting the router there)? I have 2 cables between the hallway master box and the loft, one 4 core and one 8 core telephone cable. The 4 core is currently in use with the 8 core as spare - both follow the same route and are approx 15m long.

Q3: would there be any advantage in doubling or trebling up on cores used between the current master box location and the loft splitter to reduce signal loss?

Although our BB service is rather poor (around 4Mb average) I believe this is down to our distance from the exchange on an all copper supply ATM, rather than restrictions due to internal wiring.

thanks

Phil

[Peter Crosland]

The incoming cable will almost certainly be a twisted pair but in any case you have no control over that.

It is best practice to locate the ADSL router as close to the master socket as possible and use network cable from it to the computers. Forget about the cores or the signal loss within the building as it will be negligible. The real problem within buildings is interference to the phone lines.

[Andy Burns]

Telephone cable *is* twisted pair, albeit cat3 rather than cat5 you might be used to for ethernet in office wiring, most likely the cable will be CW1308 spec internally the drop wire or underground wire may have a more substantial outer sheath.

Probably relatively little difference, though more with VDSL that you'd get from ADSL (your 15m is a greater fraction of the hundreds of metres to the cabinet that it would be of the thousands of metres to the exchange) so long your cable is twisted i.e proper phone cable, rather than e.g. alarm cable.

Doubt it, but you could try I suppose.

[Dave Liquorice]

Could try but I suspect that the impedance mismatches would screw things up. CCS "CW1308" certainly fups up ADSL. VDSL uses a much broader bandwidth (up to 30 MHz?). Those higher frequencies won't like impedance mismatches.

[thescullster]

Thanks to all

I will have to strip a bit of the existing phone cable and/or spare to check that the existing stuff is twisted pair between hall and loft.

Phil

[Dave Liquorice]

Proper telephone twisted pair (CW1308) has white/ /white for the solid core wire of each pair. The only other cable that I can think of that looks like CW1308 is alarm cable, that has plain colour, stranded, wires.

Not sure if CCA is about in CW1308 form, CCS is and upsets ADSL. Might be worth trying confirm that the wire is copper, not steel or aluminium. A magnet sorts out steel, scrapeing to check the core color copper v ali.

[meow2222]

Whats the mechanism of upset with CCS, eddy currents?

NT

[Dave Liquorice]

Donno, haven't the test kit to investigate how a signals from 125 kHz to 1.1 MHz propagate down a mix of copper and CCS.

There is a thread, probably in here from within the last year or two about it. IIRC using a length of CCS "CW1308" a handful of metres long between the incoming dropwire and internal copper CW1308 knocked the best part of 2 Mbps off the sync speed and at night it was even worse.

Again IIRC, Steel has about 7 times the resistance of copper so there was two transitions that potentially have an impedance mismatch and thus reflections etc. These reflections will interfere with the main signals.